Generally, for example, as disclosed in JP-62-095402A, an electromechanical conversion device such as a rotation angle detection device is provided to detect a rotation angle of a detection object based on a magnetic field which varies due to a rotation of the detection object. In this case, a magnetism detection element such as a Hall element is interlocked with the rotation of the detection object to relatively rotate with respect to a magnetic field generation unit such as a permanent magnet. Thus, the rotation angle detection device can detect the rotation angle of the detection object based on signals, which are outputted from the magnetism detection element and varies with the rotation of the detection object.
Moreover, it is also known a synchronous motor (being an electromechanical conversion device) which includes a stator and a rotor. The stator has a three-phase winding. The rotor has the permanent magnet or the like as the magnetic field generation unit. In this case, the rotor rotates with respect to the stator, responding to signals inputted to the stator.
However, in the electromechanical conversion device such as the rotation angle detection device and the synchronous motor, the magnetism detection element (which is electromechanical conversion unit) and the rotor relatively move with respect to the magnetic field generation unit. Thus, the magnetic field in the proximity of the electromechanical conversion unit greatly varies. Therefore, induction noise is piggybacked onto the outputted signal and the inputted signal of the electromechanical conversion unit, due to the variation of the magnetic field. As a result, for example, the error of the rotation angle detection device in detecting the rotation angle increase. The synchronous motor malfunctions.
In order to reduce the induction noise piggybacked onto the outputted signal and the inputted signal of the electromechanical conversion device, it is considered that the outputted signal and the inputted signal of the electromechanical conversion device are transferred via twisted pair cables, as disclosed in JP-10-141993A. However, because unevenness of the weaving of the signal wires cannot be completely eliminated, the noise countermeasures via the twisted pair cables is unsatisfactory in the case where the signal amplitude of the outputted/inputted signal of the electromechanical conversion device is small.